The present invention relates to the manufacture of bevel gear without machining (cutting), but using cylindrical, metallic blanks, e.g. steel blanks.
The equipment commonly used for making bevel gear has usually a lower die, which is contoured in accordance with the bevel gear to be made by forcing the blank into the die by means of a press ram or punch. The punch is, for example, guided in a coaxial sleeve or tube, in which the punch moves. Tooling of that kind is, for example, disclosed in the U.S. Pat. No. 3,731,516 by me and others. The invention relates specifically to improvements in equipment of the kind of equipment in the general sense as outlined above.
Bevel gears are, for example, made by hot forging, wherein a blank is forged by means of a punch and a die. This method does not require machining and the forging is carried out in a protective gas atmosphere. The German Pat. No. 1,048,766 discloses such a method, and the blank to be used here has a diameter which is smaller than the smallest inner diameter of the die as determining the contour of the teeth. Moreover, the blank is tapered at the end where facing the bottom of the die. It can be seen that the blank requires extensive preparations to be undertaken prior to working proper. The principal purpose of these preparations is to make sure that the teeth defining cavity portions of the die are really filled. These preparations as well as heating the blank in a protective gas are quite expensive.
My U.S. Pat. No. 3,675,459 discloses convexly contoured blanks, which though also requiring some preparations, are still less expensive to make. Such blanks can be made e.g. from sheared rods in automated cold working machines. This type of blank permits even working without heating and without a protective gas atmosphere. Still, the barrel or ball-shaped blanks do require some preparations.